The invention is directed to a new process for the production of 1-methylcyclopropanecarboxaldehyde of the formula ##STR3##
This cyclopropane derivative is an important starting material for a synthesis of isodehydroabietenolide, which in turn is an intermediate product for the synthesis of the antileukemia agent, triptolide (see J. Amer. Chem. Soc. Vol. 101, pages 7423 (1979)).
It is already known (see J. Org. Chem., Vol. 27, page 51 (1962)) to produce 1-methylcyclopropanecarboxaldehyde by reduction of 1-methylcyclopropanecarbonitrile with lithium aluminum hydride. The 1-methylcyclopropanecarbonitrile in turn can be produced (see J. Amer. Chem. Soc., Vol. 56, page 2710 (1934)) by reaction of methacrylonitrile with diazomethane. However, the conversion with diazomethane is little suited for the production on an industrial scale.
It is already known (J. Amer. Chem. Soc., Vol. 97, page 2778 (1975)) to produce 1-methylcyclopropanecarboxaldehyde by reaction of methallyl alcohol with diiodomethane and dry Zn-Cu-alloy and subsequent oxidation of the 1-methylcyclopropylcarbinol with CrO.sub.3 in pyridine. The total yield of 1-methylcyclopropanecarboxaldehyde, however, is low according to this process.